From: Tomi Valkeinen tomi.valkeinen@ideasonboard.com
[ Upstream commit 478306edc23eec4f0ec24a46222485910c66212d ]
Use the crtc_* fields from drm_display_mode, instead of the "logical" fields. This shouldn't change anything in practice, but afaiu the crtc_* fields are the correct ones to use here.
Reviewed-by: Aradhya Bhatia aradhya.bhatia@linux.dev Tested-by: Parth Pancholi parth.pancholi@toradex.com Tested-by: Jayesh Choudhary j-choudhary@ti.com Reviewed-by: Devarsh Thakkar devarsht@ti.com Link: https://lore.kernel.org/r/20250723-cdns-dsi-impro-v5-3-e61cc06074c2@ideasonb... Signed-off-by: Tomi Valkeinen tomi.valkeinen@ideasonboard.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES
Explanation
What changed - drivers/gpu/drm/tidss/tidss_crtc.c:227 switches the pixel clock programmed into the VP from `mode->clock * 1000` to `mode->crtc_clock * 1000`. This ensures the CRTC gets the adjusted pixel rate after encoder/bridge modifications. - drivers/gpu/drm/tidss/tidss_dispc.c updates all timing and size programming to use `crtc_*` fields instead of the “logical” ones: - Horizontal timings: `hfp/hsw/hbp` now computed from `crtc_hsync_start/crtc_hsync_end/crtc_hdisplay/crtc_htotal`. - Vertical timings: `vfp/vsw/vbp` now computed from `crtc_vsync_start/crtc_vsync_end/crtc_vdisplay/crtc_vtotal`. - Screen size register uses `crtc_hdisplay` and `crtc_vdisplay`. - The register writes affected include DISPC_VP_TIMING_H, DISPC_VP_TIMING_V, and DISPC_VP_SIZE_SCREEN.
Why it matters - In DRM, the `crtc_*` fields represent the timings and pixel rate that the CRTC must actually program, after any adjustments by encoders/bridges (e.g., DSI DPI conversions, double-clocking, pixel repetition, burst modes). - Using the non-crtc (“logical”) mode values can mismatch the VP’s clock and timing registers with the bridge’s expectations, causing real failures: sync lost, blank display, or unstable output. TIDSS explicitly handles sync-lost conditions elsewhere; wrong pixel clock/timings are a common source of such issues. - The change aligns TIDSS with widespread practice across DRM drivers and with cadence DSI programming, which already relies on `crtc_*` for the DPI-to-DSI path. This improves correctness when using TIDSS with DSI/LVDS bridges that adjust the mode.
Backport suitability - Bugfix: Corrects which mode members are used to program the hardware (functional correctness for any pipeline that adjusts the CRTC mode). It can solve user-visible issues (no display/sync lost) in such configurations. - Small and contained: The diff is narrowly scoped to TIDSS VP clock and timing programming; no architectural changes. - Low risk: Pure field substitution to the correct `crtc_*` members; widely used pattern in other DRM drivers. No API changes or cross- subsystem impact. - No feature additions: Behavior remains the same for pipelines where `crtc_*` equals logical fields; improves only cases where they differ. - Stable policy fit: Important correctness fix with minimal regression risk in a confined subsystem, and it does not touch core kernel or unrelated code.
Notes - Mode validation in TIDSS still checks the logical mode; while that’s unchanged here, this patch alone is safe and beneficial. If needed, further adjustments to validate the effective CRTC requirements can be considered separately.
drivers/gpu/drm/tidss/tidss_crtc.c | 2 +- drivers/gpu/drm/tidss/tidss_dispc.c | 16 ++++++++-------- 2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/tidss/tidss_crtc.c b/drivers/gpu/drm/tidss/tidss_crtc.c index a2f40a5c77030..17efd77ce7f23 100644 --- a/drivers/gpu/drm/tidss/tidss_crtc.c +++ b/drivers/gpu/drm/tidss/tidss_crtc.c @@ -225,7 +225,7 @@ static void tidss_crtc_atomic_enable(struct drm_crtc *crtc, tidss_runtime_get(tidss);
r = dispc_vp_set_clk_rate(tidss->dispc, tcrtc->hw_videoport, - mode->clock * 1000); + mode->crtc_clock * 1000); if (r != 0) return;
diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c index c0277fa36425e..3f6cff2ab1b29 100644 --- a/drivers/gpu/drm/tidss/tidss_dispc.c +++ b/drivers/gpu/drm/tidss/tidss_dispc.c @@ -1215,13 +1215,13 @@ void dispc_vp_enable(struct dispc_device *dispc, u32 hw_videoport,
dispc_set_num_datalines(dispc, hw_videoport, fmt->data_width);
- hfp = mode->hsync_start - mode->hdisplay; - hsw = mode->hsync_end - mode->hsync_start; - hbp = mode->htotal - mode->hsync_end; + hfp = mode->crtc_hsync_start - mode->crtc_hdisplay; + hsw = mode->crtc_hsync_end - mode->crtc_hsync_start; + hbp = mode->crtc_htotal - mode->crtc_hsync_end;
- vfp = mode->vsync_start - mode->vdisplay; - vsw = mode->vsync_end - mode->vsync_start; - vbp = mode->vtotal - mode->vsync_end; + vfp = mode->crtc_vsync_start - mode->crtc_vdisplay; + vsw = mode->crtc_vsync_end - mode->crtc_vsync_start; + vbp = mode->crtc_vtotal - mode->crtc_vsync_end;
dispc_vp_write(dispc, hw_videoport, DISPC_VP_TIMING_H, FLD_VAL(hsw - 1, 7, 0) | @@ -1263,8 +1263,8 @@ void dispc_vp_enable(struct dispc_device *dispc, u32 hw_videoport, FLD_VAL(ivs, 12, 12));
dispc_vp_write(dispc, hw_videoport, DISPC_VP_SIZE_SCREEN, - FLD_VAL(mode->hdisplay - 1, 11, 0) | - FLD_VAL(mode->vdisplay - 1, 27, 16)); + FLD_VAL(mode->crtc_hdisplay - 1, 11, 0) | + FLD_VAL(mode->crtc_vdisplay - 1, 27, 16));
VP_REG_FLD_MOD(dispc, hw_videoport, DISPC_VP_CONTROL, 1, 0, 0); }